Onboard air

[tewlman]

Has anyone ever tried using a 20 oz. paintball CO2 tank for an onboard air application?

Any experience or pros and cons????

Obviously you couldn't air too many tires, but I bet it could get you thru a couple of wheelin trips.

 

[theo]

Depends on pressure. "According to my calculations" you would need ~700 psi in your CO2 bottle to fill ONE 30 x 10 x 15 tire to 20 psi. That means you need 2800 psi to fill 4. I doubt your bottle is higher pressure than that.

How's my math?

 

[tewlman]

how are you coming up with your figures?? ???

 

[RHINO]

ya know they have little tiny bottles at the weld shop, i dont remember the poundage but i aired up my rig 3 times from 12 to 30 PSI when i tested it out.

 

[Outback]

I wouldn't use paintball cylinders. As stated, they don't hold much. Maybe as a last-resort to get you partially going.

I know of a better way...


Jody. [tt]See sig line below...[/tt]

 

[theo]

[quote author=tewlman link=board=1;threadid=9901;start=msg87772#msg87772 date=1073680466]
how are you coming up with your figures?? ???
[/quote]

P1V1 = P2V2

want to know P1 (pressure in CO2 bottle)
V1 = 20 oz.
P2 = 20 psi (or whatever pressure you want in your tire)
V2 = tire volume (volume of a toroid (donut) = pi(R^2-r^2)w
and some unit conversions

assumptions and omissions:
-30x10x15 tire size
-the toroid volume is an approximation, I think, derived from the definite integral that is more exact.
-auto tires aren't perfect toroids
-you can only fill until the pressures are equal, so you don't get all of the air in the bottle

Basically, you just calculate how much volume you need and how much you have available. Clear as mud now, right?

 

[IDave]

Damn! I remember having to do all that once upon a time.

 

[theo]

Actually, I just realized I got the oz. to cubic inch conversion wrong. The "new" result is ~600 psi to fill one tire. So only 2400 to fill all 4. By tomorrow I'll have you floating a hot air balloon with your paintball bottle!

 

[theo]

[quote author=theo link=board=1;threadid=9901;start=msg87883#msg87883 date=1073690504]
Actually, I just realized I got the oz. to cubic inch conversion wrong. The "new" result is ~600 psi to fill one tire. So only 2400 to fill all 4. By tomorrow I'll have you floating a hot air balloon with your paintball bottle!
[/quote]

No wait! How many cubic inches in an ounce? First I used 29.6. Then I changed it to 36. But there's no way. I started thinking of the size of an ounce of Jack Daniels. About an inch in a shot glass, right? That means a fluid ounce is somewhere around 1 or 2 cubic inches. In fact, it's 1.8 cubes.

Plus, I'm not sure about the toroid volume formula. Maybe I better look into it some. Give me the weekend to clear the cobwebs and I'll get back to y'all.

Sorry about that.
theo :-[

 

[Poser]

Too much messing around for the lack of volume in a paintball cyl.

Get a real CO2 cyl and be done with it, if that is the direction you want to go.

Good luck!

-Steve

 

[tewlman]

i've got a 20 lb bottle that works great, I was just thinking of a slick space saving way to air up.

Theo, good luck with your numbers. I'll have a few beers and try to theorize the meaning of life......

Wait, I think I have it!!!!

Work as little as possible, make lots of money, and spend it on the cruiser so I can wheel every weekend.

 

[rgentry]

I think something is missing here. Isn't the CO2 stored in the tank
in a liquid form? If so, then using the ideal gas law isn't going to
give you the information you need to figure out how many tires
you can fill up. That's the beauty of CO2; much more stored
gas than is implied by the tiny bottle.

 

[stainless40]

??? OK guys I hate to brake it to you, but...your math is not relative here. CO2 is a liquid in its stored pressurized state. It works off head pressure from the liquid and as its released from its pressurized state it returns to a gas. This is why your high pressue guage reads the same pressure untill the bottle is empty. It is not the same as compressed air, which starts to lose pressure as soon as you start to use it. By the way (plug) I sell CO2 bottles at the best prices around. If you would like to know more about your bottle or the products I offer you can contact me direct @ eddraves@earthlink.net

 

[IDave]

Yoh, Stainless. You of all people should be able to tell us the answer to the originial question! ???

 

[stainless40]

What was the orig queston??Oh Yeah.. less then 1lb. about 4 blow up trunk spares,maybe 2-31's and I doubt 1-44"er. It would work OK for air lockers, but forget about any power tools.

 

[CruisinGA]

I bet a 20- ouncer would work pretty well for a toolbox emergency source.

 

[JK]

I think everybody is partially right! The 20oz rating on the CO2 bottle is a liquid volume capacity. The conversion from US-Fluid Onces to Cubic Inches is:

1 Fluid Once = 1.80469 cubic inches

The 20oz bottle has an approximate internal volume of
40 cubic inches (assuming a 10% head space in the bottle) at atmospheric pressure (14.7 psia). With this information you can use Theo's formula (Boyle's Law) to obtain the final volume at an elevated pressure. I roughly estimate a 31x10.5-15 to have an internal volume of 5,000 cubic inches at atmospheric pressure (14.7 psia).
DO NOT exceed the stamped pressure rating on the bottle, I have seen high pressure pipe failures in petrochemical facilities and it is not a pretty site.Hope this helps
Good Luck,
JK

 

[Degnol]

Boyles and Charles are banging the back of my bald head...
PV=nrT. Does that look like an abbreviation for PERVERT????
I am impressed with everybody's understanding of the gas laws and their practical application, REALLY. I learned something tonight, namely that I WASN'T drunk the night before my gass bottle on my welder went from 5000# to almost 0# overnight!!! I did NOT leave it on after all.
Seriously, get a small CO2 bottle and stow it. You can inflate eleventyseven tires with it.
Ed Long

 

[JK]

Are you sure Degnol you weren't Drunk?

 

[tewlman]

well you guys have shown you that you stayed awake in school, but I think the only way to find out for sure is to try it out.
probably the only thing i'll need to do is make or buy an adapter, because the paintball CO2 has a different fitting than the larger ones. I already have a regulator.
I will get back with the results when I have completed the testing in proper form.

Steve